In general, mobile communication systems are developed to provide mobility of communications to users. The mobile communication system makes rapid technical advance and provides a high speed data communication service as well as voice communications.
As one of next-generation mobile communication systems, 3rd Generation Partnership Project (3GPP) is working on the standardization of Long Term Evolution (LTE). An LTE system, which aims for its commercialization in about 2010, is to provide a high speed packet based service of a data rate of about 100 Mbps at maximum higher than the data rate currently serviced.
To provide the high speed packet based service of the data rate of about 100 Mbps at maximum, a method for reducing the number of nodes in a communication path by simplifying a network structure or a method for making wireless protocols close to the wireless channel as much as possible is under discussion.
Meanwhile, the data service, unlike the voice service, in the mobile communication system determines the allocable resources based on the data amount to transmit and the channel status. The wireless communication system such as mobile communication system performs management to allocate the transmission resource by taking into account the resource amount to transmit at from scheduler, the channel status, and the data amount. This also applies to the LTE which is one of the next-generation mobile communication systems. That is, in the LTE system, the scheduler of a base station manages and allocates the wireless transmission resources.
The wireless communication system such as mobile communication system separates a forward transmission and a reverse transmission based on the transmission direction of the data. The forward direction indicates the direction from the base station to a terminal, and the reverse direction indicates the direction from the terminal to the base station.
In the forward transmission, the base station can accurately determine the data amount to transmit. Since the base station can accurately determine the channel status, the resource amount, and the amount of the data to transmit, the scheduler can normally accomplish the scheduling.
However, in the allocation of the reverse wireless transmission resource, the scheduler of the base station may allocate the resource while not accurately detecting a buffer status of the terminal.
In the LTE system, the terminal reports the buffer status to the base station using a buffer status report control element. The buffer status report control element is transmitted only when a particular condition is satisfied. As a result, the base station cannot accurately know the buffer status of the terminal all the time.